Vertical Bridgman furnace thermal field regulation device and regulation method

Abstract

This invention discloses a vertical Bridgeman furnace thermal field control device and method, relating to the field of crystal growth technology. The device includes: a furnace body, a vertically arranged cylindrical structure; a crucible, which moves up and down along the central axis of the furnace body; a heating device located in the upper part of the furnace body; a cooling device located on the bottom wall of the furnace body; a heat-insulating cavity located at the center of the bottom of the furnace body and above the cooling device, with its outer periphery covered by heat-insulating material; and an opening and closing device located directly above the heat-insulating cavity, having open and closed states, including a rotatable central support and multiple shielding components, with a pressure regulating hole on the central support. The method includes: closing the opening and closing device during the raw material melting stage; opening the opening and closing device during the crystal growth stage, activating the cooling device to establish a temperature gradient, and lowering the crucible to grow the crystal; closing the opening and closing device after the crystal enters the heat-insulating cavity; and adjusting the cooling device and the opening and closing device to control the crystal cooling. This invention can shorten the furnace body length, achieve precise temperature gradient control, and improve crystal quality.

Description

Technical Field

[0001] This invention relates to the field of crystal growth technology, and in particular to a method for controlling the temperature gradient and residual heat inside a short furnace using the Vertical Bridgman Method (VB). Background Technology

[0002] The Vertical Bridgman (VB) process is a commonly used crystal growth method for preparing large-size semiconductor single crystals. This method involves placing a heating device at the top of the furnace to heat and melt the raw material placed in a crucible, simultaneously creating an axial temperature gradient within the furnace. By controlling the relative movement of the crucible and the temperature field, the melt gradually solidifies from the high-temperature region to the low-temperature region, thus achieving directional crystal growth and forming high-quality single crystals. Existing VB furnaces mainly rely on arranging multiple heating zones and insulation structures along the furnace axis, increasing the furnace length to create the required temperature gradient distribution. Therefore, to obtain a stable and sufficiently wide temperature gradient region, a relatively long furnace structure is usually required, resulting in a large overall equipment size, large space occupation, and high manufacturing costs. Secondly, the existing temperature gradient is mainly achieved through zoned heating power and fixed heat insulation structure. Its temperature field distribution is relatively fixed, making it difficult to finely adjust the magnitude and distribution shape of the temperature gradient, which in turn affects the stability of the solid-liquid interface and the quality of crystal growth. In addition, after the crystal growth is completed, there is still a high residual temperature in the furnace, which leads to the accumulation of internal stress and the generation of defects in the crystal, as well as a long waiting time for the furnace to be opened, thus affecting the crystal production efficiency.

[0003] Therefore, there is an urgent need for a technical solution that can achieve efficient and controllable temperature gradient distribution with a shorter furnace structure, and avoid the influence of residual heat after crystal growth. This would promote the further application and development of the vertical Bridgman process in semiconductor crystal growth. Summary of the Invention

[0004] The purpose of this invention is to provide a vertical Bridgman furnace thermal field control device and control method, which aims to solve the problems of excessive length of existing vertical Bridgman furnaces, difficulty in accurately controlling temperature gradients, and the impact of residual heat on crystal quality.

[0005] The technical solution of the present invention is as follows: A first aspect of the present invention provides a vertical Bridgeman furnace thermal field control device, comprising: The furnace body is a vertically arranged cylindrical structure; A heating device is installed in the upper part of the furnace body for heating the crystal growth raw materials; A crucible, arranged along the central axis of the furnace body, can be moved vertically up and down within the furnace body and is used to hold raw materials for crystal growth. A cooling device is installed on the bottom wall of the furnace body to actively cool the bottom of the furnace body, so as to form a low temperature zone at the bottom of the furnace body and together with the heating device to form a temperature gradient distributed along the axial direction. The heat insulation cavity is fixedly installed at the center of the bottom of the furnace body and above the cooling device. It is a cavity structure with an open top and its outer periphery is covered with heat insulation material. The crucible can be lowered into the heat insulation cavity. An opening and closing device is located directly above the insulation cavity and has an open and closed state. The opening and closing device includes a rotatable central support and multiple shielding members distributed circumferentially around the central support. The shielding members are linked to the central support; when the central support rotates, the shielding members retract towards the central support or expand outward to adjust the size of the central opening of the opening and closing device. The central support is provided with an air pressure regulating hole for connecting the upper and lower spaces of the opening and closing device. In the open state, the central opening of the opening and closing device allows the crucible to pass through; in the closed state, the central opening of the opening and closing device is closed, providing thermal insulation between the upper and lower parts of the furnace body.

[0006] Furthermore, the furnace body is provided with an air inlet, which is located above the opening and closing device and is used to introduce protective gas into the furnace.

[0007] Furthermore, a thermocouple is provided at the bottom of the crucible to detect temperature changes near the crystal's descent path.

[0008] Furthermore, a hollow support rod is provided through the center of the insulation cavity, and the crucible is placed at the upper end of the hollow support rod and can descend into the insulation cavity with the hollow support rod.

[0009] Furthermore, the furnace body and the insulation cavity are any one of the following shapes: cylindrical, polygonal, wide at the top and narrow at the bottom, or narrow at the top and wide at the bottom.

[0010] Furthermore, the heat insulation material is thermal insulation cotton; the thermal insulation cotton is alumina fiber, zirconium oxide fiber, ceramic fiber cotton, high-temperature insulation cotton, or refractory fiber cotton.

[0011] Furthermore, the plurality of blocking members are symmetrically distributed circumferentially along the central support member, and can synchronously retract towards the center or expand outward to continuously adjust the size of the central opening of the opening and closing device; the central support member is provided with a guide structure for guiding the movement of the blocking members, and the guide structure is any one of the following: oblique guide groove, arc guide groove, curved guide groove, radial guide groove, annular guide rail, segmented guide rail or cam-type guide structure.

[0012] Furthermore, the shielding component is a blade, the upper end face of the central support component is provided with multiple oblique guide grooves, and the lower end face is provided with a slide rail; the two ends of the blade are respectively slidably engaged with the oblique guide grooves and the slide rail, and when the central support component rotates, the blade is driven to retract towards the center or expand outward; the number of blades is not less than two, and the blade is any one of a fan-shaped plate, an arc plate, a trapezoidal plate, or a fan-shaped annular plate.

[0013] Furthermore, the adjacent shielding components cooperate in the closed state by edge fitting, edge overlapping, partial overlap, or maze-like misalignment shielding to reduce the heat exchange channel between the central area and the upper space after closure.

[0014] Furthermore, the pressure regulating hole is configured as one or multiple holes distributed symmetrically along the center or circumferentially, and the pressure regulating hole is any one of a round hole, an oblong hole, an elongated hole, or a multi-hole array.

[0015] Furthermore, both the upper and lower surfaces of the opening and closing device are covered with heat-insulating cotton.

[0016] Furthermore, the opening and closing device also includes a drive mechanism, the output end of which is connected to the central support member and is used to drive the central support member to rotate around the central axis of the furnace body.

[0017] Furthermore, the driving mechanism is any one of a mechanical transmission mechanism, an electric transmission mechanism, a pneumatic transmission mechanism, a hydraulic transmission mechanism, or a magnetic coupling transmission mechanism.

[0018] Furthermore, the cooling device includes an inlet, a cooling pipe, and an outlet. The inlet and outlet are located on the side wall of the furnace body, and the cooling pipe is laid on the bottom wall of the furnace body to allow the cooling medium to flow and exchange heat at the bottom of the furnace body.

[0019] Furthermore, the cooling pipes are arranged in a serpentine pattern, and the middle area is adapted to the shape of the bottom of the insulation cavity, so as to allow the cooling medium to flow and exchange heat at the bottom of the furnace body; the cooling medium is any one of cooling gas, cooling liquid, heat transfer oil, water or refrigerant.

[0020] Furthermore, the cooling device also includes a flow regulating valve and a temperature sensor. The flow regulating valve is located at the inlet or inlet pipe of the cooling device, and the temperature sensor is located at the outlet of the cooling device.

[0021] A second aspect of the present invention provides a method for thermal field control using the above-described apparatus, comprising the following steps: S1. Raw material melting stage: Control the opening and closing device to be in the closed state so that the heat is concentrated in the upper part of the furnace body to heat and melt the raw materials in the crucible; S2. Crystal growth stage: Control the opening and closing device to switch to the open state, start the cooling device, and form a low temperature zone at the bottom of the furnace body, which together with the heating device to build a temperature gradient distributed along the axis; at the same time, the crucible is lowered along the axis, and the melt gradually solidifies and grows crystals under the action of the temperature gradient. S3. Thermal field isolation stage: After the crystal growth is completed and it enters the insulation chamber with the crucible, the opening and closing device is switched to the closed state to prevent the residual heat in the upper part of the furnace from being transferred downwards. S4. Cooling control stage: Adjust the cooling intensity of the cooling device and the opening and closing size of the opening and closing device to control the cooling rate of the crystal.

[0022] Furthermore, the cooling intensity is adjusted by a flow regulating valve installed at the inlet of the cooling device or on the inlet pipe, and a temperature sensor installed at the outlet of the cooling device.

[0023] Furthermore, the crystal is a gallium oxide single crystal.

[0024] The beneficial technical effects of the present invention are as follows: This invention features a heat-insulating cavity at the bottom of the furnace body, with an openable / closable device above it. When the crystal descends into the heat-insulating cavity with the crucible, the device closes, isolating the crystal growth area from the high-temperature area at the top of the furnace. The heat-insulating cavity is surrounded by insulating cotton, and the upper and lower surfaces of the opening / closing device are also covered with insulating cotton. This effectively prevents residual heat from being transferred downwards, reduces the continuous effects of high-temperature radiation and heat convection on the grown crystal, avoids the crystal being exposed to a high-temperature environment for an extended period after detaching from the growth interface, reduces thermal hysteresis and additional thermal stress during crystal cooling, and improves crystal quality.

[0025] During the raw material melting stage, closing the opening and closing device allows heat to be concentrated in the upper part of the furnace body, unaffected by the bottom cooling device, effectively maintaining high temperature to accelerate raw material melting, improve heating efficiency, and reduce energy consumption.

[0026] The present invention provides a cooling device at the bottom of the furnace body, with cooling pipes evenly distributed in a serpentine pattern on the bottom wall of the furnace body. This allows for active cooling of the bottom area of ​​the furnace body, establishing and adjusting the temperature gradient. It eliminates the need to rely on extending the furnace body length to achieve natural cooling, thereby meeting the temperature gradient requirements for crystal growth under shorter furnace body conditions and reducing equipment manufacturing costs.

[0027] By adjusting the flow rate of the cooling medium and monitoring the output temperature using a temperature sensor, the bottom temperature gradient can be controlled based on the crystal's descent position and cooling status, creating a controllable cooling environment. The cooling device and the opening / closing device work together to regulate the flow rate and temperature of the cooling medium, as well as the opening / closing size of the device, enabling further fine control of the temperature gradient.

[0028] This invention achieves precise control of the temperature gradient and effective isolation of the environment after crystal growth by coordinating the insulation cavity, opening and closing device and cooling device. It reduces the dependence of furnace length on temperature gradient, reduces stress and defects caused by residual heat, and is conducive to the preparation of high-quality crystals. Attached Figure Description

[0029] Figure 1 This is a cross-sectional schematic diagram of the vertical Bridgeman furnace thermal field control device in an embodiment of the present invention; Figure 2 This is a schematic diagram of the opening and closing device according to an embodiment of the present invention; Figure 3 This is an exploded view of the opening and closing device according to an embodiment of the present invention; Figure 4 This is a top view of the cooling structure according to an embodiment of the present invention; The labels in the attached diagram: 1. Pressure relief hole, 2. Furnace body, 3. Heating rod support, 4. Heating rod, 5. Air inlet, 6. Insulation cotton, 7. Air pressure regulating hole, 8. Insulation cavity, 9. Input port, 10. Cooling pipe, 11. Crucible, 12. Thermocouple, 13. Central support, 14. Hollow support rod, 15. Output port, 16. Angled guide groove, 17. Slide rail, 18. Blade, 20. Opening and closing device, 21. Cooling device. Detailed Implementation

[0030] This invention provides a structure that isolates semiconductor crystals from residual heat in the furnace after growth, solving the problem of increased internal stress and defects in the crystal caused by residual heat in the furnace. Figure 1 As shown, the structure includes: The furnace body 2, in this embodiment, is a cylindrical structure. A pressure relief hole 1 is provided at the top of the furnace body 2 to release pressure during internal temperature changes and gas thermal expansion, maintaining a stable pressure difference between the inside and outside of the furnace. A heat insulation layer is provided on the sidewalls of the furnace body 2, formed by filling with heat-insulating cotton 6, to reduce heat loss during furnace operation and improve thermal stability. A heating device for crystal growth is provided inside the furnace body 2. The heating device includes a heating rod support 3 and several heating rods 4 mounted on the heating rod support 3. The heating rods 4 are distributed circumferentially around the crucible 11 to provide the heat required for crystal growth to the raw material melt inside the crucible 11. The heating rods 4 and the heating rod support 3 can adopt conventional structures in the art, and their specific structures and installation methods are not considered limiting aspects of this invention. The crucible 11 is located in the central axial region inside the furnace body 2 and is used to hold the oxide crystal raw material to be grown. A thermocouple 12 is positioned close to the center of the bottom of the crucible 11 to detect temperature changes near the crystal's descent path, allowing for monitoring and adjustment of the subsequent cooling process.

[0031] The insulation cavity 8 is located at the bottom center of the furnace body 2, through which a hollow support rod 14 passes, and is covered with insulation cotton 6 on the outside to reduce heat exchange between the insulation cavity 8 and the bottom cooling device and the top high-temperature area.

[0032] Opening and closing device 20, such as Figure 2 , Figure 3 The structure includes: The upper surface of the central support member 13 has six circumferentially evenly distributed oblique guide grooves 16, each extending at a 30° angle to its radial centerline. The lower surface of the central support member 13 has a hexagonal slide rail 17. Correspondingly, there are six blades 18, each with an upper sliding pin and a lower sliding pin at its upper and lower ends, respectively. The upper sliding pin is slidably engaged within the corresponding oblique guide groove 16, and the lower sliding pin is slidably engaged within the hexagonal slide rail 17. The central support member 13 is positioned directly above the insulation cavity 8, with a pre-set distance of 10cm between them. Both the upper and lower surfaces of the opening and closing device 20 are covered with insulation cotton 6. In addition, a pressure regulating hole 7 is provided through the plate surface of the central support member 13. The pressure regulating hole 7 passes through the heat insulation cotton 6 and is used to connect the upper and lower chamber spaces of the opening and closing device, so as to keep the air pressure on both sides in dynamic balance, thereby preventing the device from deforming or jamming or the internal hot field airflow from being disordered due to the pressure difference in a high-temperature sealed environment.

[0033] An air inlet 5 is provided on the furnace body. The air inlet 5 is located 10cm above the opening and closing device 20 and is used to introduce oxygen into the furnace in order to maintain and regulate the oxygen atmosphere inside the furnace.

[0034] In this embodiment, an adjustable thermal barrier is formed by the cooperation of the central support 13, the oblique guide groove 16, and the blades 18. When the crystal descends with the crucible 11 into the insulation chamber 8, the opening and closing device 20 closes, and together with the covering structure formed by the insulation cotton 6, a physical isolation layer is constructed between the high-temperature zone and the cooling zone of the furnace. This structure effectively blocks the downward transfer of heat radiation and convection from the high-temperature zone, reducing the secondary heating of the grown crystal by residual heat. This instantaneous thermal field isolation can significantly reduce the thermal hysteresis effect during crystal cooling, making the temperature gradient inside the crystal more linear. Furthermore, the opening and closing device also plays a crucial role in the initial preparation stage of crystal growth. During the raw material melting stage, by closing the blades 18, heat is locked in the upper region of the furnace 2, reducing ineffective heat loss to the bottom cooling device. This heat concentration effect significantly improves heating efficiency, shortens the melting time of the raw materials, reduces equipment energy consumption, and saves costs. In addition, a pressure regulating hole 7 is provided through the central support 13, allowing the upper and lower chambers isolated by the blades 18 to achieve gas flow balance. Besides the pressure difference caused by the localized thermal expansion of the gas, this invention prevents the compressive stress on mechanical moving parts caused by the pressure difference, avoiding mechanical jamming or structural deformation at high temperatures. Furthermore, the stable gas pressure environment reduces turbulence or airflow disturbances caused by sudden pressure changes, ensuring the microscopic stability of the thermal field near the growth interface. This invention constructs a precision thermal barrier and gas path balance system with dynamic control capabilities through the coordinated operation of the central support, oblique guide grooves, and blades, achieving a high degree of synergy between the thermal field, flow field, and mechanical structure. In the later stages of crystal growth, the coupling of this device with the insulation cavity effectively blocks the downward transfer of residual heat from the high-temperature region, significantly reducing the thermal hysteresis effect and linearizing the temperature gradient within the crystal, thereby suppressing crystal defects caused by thermal stress at the source. During the melting stage, its closed state achieves precise heat concentration, greatly improving heating efficiency and reducing energy consumption. Meanwhile, the dynamic balancing effect of the pressure regulating orifice not only eliminates the compressive stress of pressure difference on mechanical moving parts, effectively avoiding mechanical jamming and structural deformation at high temperatures, but also ensures the microscopic stability of the thermal field near the growth interface by reducing airflow turbulence. In summary, the thermal field structure provided by this invention not only has a significant heat preservation effect and excellent temperature field distribution, but also fundamentally ensures a smooth transition of the crystal growth interface, thereby producing semiconductor crystals with low defect surface density and excellent quality.

[0035] Specifically, during the crystal's descent into the insulation chamber, without the central support 13 and blades 18 of this invention, the high-temperature radiation from the upper part of the furnace would directly act on the grown crystal, causing a severe radial temperature difference between the crystal surface and the core. This invention, through the centripetal closure of the blades, physically cuts off the heat radiation path, placing the crystal in a relatively constant-temperature "blackbody environment." Simultaneously, if the central support does not have the pressure regulating hole 7, the localized pressure buildup during closure would interfere with the smoothness of the airflow at the growth interface; however, the presence of the pressure regulating hole 7, through instantaneous pressure relief and airflow guidance, ensures that the airflow vector direction at the growth interface does not shift during blade movement, thereby maintaining the smoothness of the crystal growth interface.

[0036] In this invention, the opening and closing principle of the opening and closing device can be referred to the appendix. Figure 2 External power is input via drive shaft 19, driving the central support 13 to rotate around its central axis. Several blades 18 are arranged at intervals along the circumference of the device, each blade 18 forming a constraint with the central support 13 and fixed components. One end of each blade 18 has a sliding fit with the slide rail 17 on the central support 13, while the other end has a limiting fit through the oblique guide groove 16. Because the blade 18 is simultaneously constrained by both the drive of the slide rail 17 and the limiting of the oblique guide groove 16, it cannot perform a full circumference rotation during the rotation of the central support 13; instead, it can only slide and rotate relative to each other along a predetermined trajectory.

[0037] When the drive shaft 19 drives the central support 13 to rotate in one direction, the slide rail 17 pushes each blade 18 to synchronously retract towards the center of the device, with adjacent blades 18 overlapping each other, causing the area of ​​the central through hole to gradually decrease until a closed state is formed. When the central support 13 rotates in the opposite direction, each blade 18 retracts in the opposite direction, and the area of ​​the central through hole gradually increases, thereby realizing the opening of the device. Thus, the rotational motion of the external power input is converted into the synchronous radial retraction and extension motion of multiple blades 18, thereby realizing the continuous adjustment of the opening size of the device and the control of opening and closing.

[0038] In some embodiments, the furnace body 2 and the insulation cavity 8 can be cylindrical, polygonal, cylindrical with a wider top and narrower bottom, cylindrical with a narrower top and wider bottom, or other enclosure structures adapted to the crystal's descent path.

[0039] In some embodiments, the material of the thermal insulation cotton 6 may be selected from at least one of alumina fiber, aluminosilicate fiber, mullite fiber, zirconia fiber, ceramic fiber cotton, high-temperature insulation cotton and refractory fiber cotton, but is not limited thereto.

[0040] In some embodiments, the opening diameter of the hinge structure is 5% to 10% larger than the crucible diameter. In some implementations, the shielding component in the opening and closing device 20 is not limited to a blade-type structure, but may also be a split-type baffle, an arc-shaped baffle, a spliced ​​baffle, a flip-type baffle, or other split-type shielding components that can achieve switching between opening and closing of the central area.

[0041] In some embodiments, the number of blades 18 corresponds one-to-one with the number of oblique guide grooves 16, and they are symmetrically distributed along the circumference. The number of blades 18 and oblique guide grooves 16 can be 2, 3, 4, 6, 8 or more.

[0042] In some embodiments, the blade 18 may be a fan-shaped plate, an arc-shaped plate, a trapezoidal plate, a fan-shaped annular plate, or other plate-shaped components suitable for converging towards the center.

[0043] In some embodiments, adjacent blades 18 can be fitted together in a closed state by means of edge fitting, edge overlapping, or partial overlap to achieve effective sealing, thereby reducing the heat exchange channel between the central region and the upper space after closure.

[0044] In some embodiments, the central support 13 is provided with a guide structure for guiding the movement of the blades 18. The guide structure may include an oblique guide groove, an arc-shaped guide groove, a curved guide groove, a radial guide groove, an annular guide rail, a segmented guide rail, or a cam-type guide structure. Any embodiment of the present invention that can achieve the synchronous retraction or synchronous deployment of multiple blades 18 is an optional embodiment.

[0045] In some embodiments, a pressure regulating hole 7 is provided through the central support member 13 to connect the upper and lower chamber spaces of the opening and closing device 20. In other embodiments, the pressure regulating hole 7 may be a single hole or multiple holes distributed symmetrically along the center or circumferentially.

[0046] In some embodiments, the pressure regulating hole 7 may be a round hole, an oblong hole, an elongated hole, a multi-hole array, or other through-hole structures that can achieve interconnection and pressure relief.

[0047] In some embodiments, the opening and closing device 20 can drive the blades 18 to open and close via mechanical transmission. In other embodiments, the opening and closing device 20 can also achieve the linkage of multiple blades 18 through a linkage mechanism, a pull rod mechanism, a gear mechanism, a cam mechanism, an electric actuator, a pneumatic actuator, a hydraulic actuator, or a magnetic coupling drive mechanism.

[0048] In some embodiments, the air inlet 5 can be located 5cm, 10cm, 15cm or other distances above the opening and closing device 20.

[0049] Meanwhile, embodiments of the present invention also provide a temperature gradient growth method, which employs, as follows: Figure 4 The structure shown is implemented as follows. The cooling device 21 is located at the bottom of the furnace body 2. The side wall of the furnace body 2 has an inlet 9 and an outlet 15. The cooling medium enters the cooling device 21 through the inlet 9, flows through the cooling pipe 10, and is discharged through the outlet 15. The cooling pipe 10 is specifically shown in the attached figure. Figure 4 As shown, the materials are evenly laid in a serpentine pattern at the bottom of the furnace body 2, and the middle area is adapted to the shape of the bottom of the insulation cavity 8.

[0050] During crystal growth, a cooling medium is introduced into the cooling device 21 to actively cool the bottom of the furnace body 2, forming a low-temperature zone at the bottom. This, combined with the opening and closing device 20, establishes an axially distributed temperature gradient between the furnace body and the upper heating zone, thus meeting the temperature field distribution requirements of the crystal growth process. Because the temperature gradient is constructed using active cooling, there is no need to rely on extending the furnace body for natural cooling. Therefore, the required temperature gradient can be formed with a shorter furnace body, which helps to shorten the furnace length and reduce equipment manufacturing costs.

[0051] In some embodiments, the cooling pipes can be evenly distributed at the bottom of the furnace, such as serpentine reciprocating distribution, spiral winding distribution, ring array distribution, parallel straight line distribution, broken line distribution, grid cross distribution, radial distribution, concentric ring distribution, zoned loop distribution, etc.

[0052] In some embodiments, the cooling medium may be a liquid, gas, or other fluid material that can absorb heat.

[0053] In some embodiments, the short furnace structure can be used for the growth and preparation of gallium oxide single crystals. Gallium oxide, as a wide bandgap semiconductor material, has high breakdown field strength and a wide bandgap, and has promising applications in power electronic devices, ultraviolet detectors, and other fields. Using the thermal field structure provided by this invention for crystal growth is beneficial for obtaining high-quality gallium oxide single crystals.

[0054] In summary, this invention provides a vertical Bridgeman furnace thermal field control device and method. By setting an insulation cavity at the bottom of the furnace body and an opening and closing device above the insulation cavity, an effective thermal barrier is formed between the high-temperature zone and the cooling zone when the crystal descends into the insulation cavity after growth. This reduces the secondary heating of the grown crystal by residual heat in the furnace, reduces the thermal hysteresis effect during crystal cooling, and minimizes the generation of internal thermal stress and defects in the crystal. Simultaneously, by setting a pressure regulating hole on the central support, the upper and lower chambers of the opening and closing device maintain a dynamic balance of air pressure, avoiding mechanical jamming, structural deformation, and airflow turbulence caused by local pressure differences, thus helping to maintain the thermal field stability during crystal growth. Furthermore, by setting a cooling device at the bottom of the furnace body and circulating the cooling medium through the inlet, cooling pipes, and outlet, a low-temperature zone can be actively constructed at the bottom of the furnace body, forming an axially distributed temperature gradient with the upper heating zone. This satisfies the temperature field distribution requirements for crystal growth with a shorter furnace body, reduces dependence on natural cooling length, and lowers equipment size and manufacturing costs. Furthermore, during the raw material melting stage, the closing of the opening and closing device reduces heat loss to the lower part of the furnace, allowing heat to accumulate in the upper region, improving heating efficiency and reducing energy consumption. Thus, this invention, through the synergistic design of insulation structure, opening and closing control, and active cooling, systematically improves problems such as residual heat transfer, temperature gradient control, and gas pressure balance during vertical Bridgman crystal growth, which is beneficial for obtaining semiconductor crystals with lower defect density and higher quality. It should be understood that the application of this invention is not limited to the examples described above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A vertical Bridgeman furnace thermal field control device, characterized in that, include: The furnace body is a vertically arranged cylindrical structure; The crucible, positioned along the central axis of the furnace body, can move vertically up and down within the furnace body. Used to hold raw materials for crystal growth; A heating device is installed in the upper part of the furnace body for heating the crystal growth raw materials; A cooling device, installed on the bottom wall of the furnace body, is used to actively cool the bottom of the furnace body to prevent the furnace from overheating. A low-temperature zone is formed at the bottom of the body, and together with the heating device, it forms a temperature gradient distributed along the axial direction. The heat insulation cavity is fixedly installed at the center of the bottom of the furnace body and above the cooling device, and is open at the top. The cavity structure of the mouth is covered with heat-insulating material on its outer periphery, and the crucible can be lowered into the heat-insulating cavity; An opening and closing device is located directly above the insulation cavity and has an open and closed state. The opening and closing device includes a rotatable central support and multiple shielding members distributed circumferentially around the central support. The shielding members are linked to the central support; when the central support rotates, the shielding members retract towards the central support or expand outward to adjust the size of the central opening of the opening and closing device. The central support is provided with an air pressure regulating hole for connecting the upper and lower spaces of the opening and closing device. In the open state, the central opening of the opening and closing device allows the crucible to pass through; In the closure In this state, the central opening of the opening and closing device is closed, providing thermal insulation between the upper and lower parts of the furnace body.

2. The vertical Bridgeman furnace thermal field control device according to claim 1, characterized in that, A hollow support rod is inserted through the center of the insulation cavity, and the crucible is placed at the upper end of the hollow support rod and can descend into the insulation cavity with the hollow support rod.

3. The vertical Bridgeman furnace thermal field control device according to claim 1, characterized in that, The plurality of shielding members are symmetrically distributed circumferentially along the central support member and can be synchronously retracted towards the center or expanded outward to continuously adjust the size of the central opening of the opening and closing device.

4. The vertical Bridgeman furnace thermal field control device according to claim 3, characterized in that, The central support member is provided with a guide structure for guiding the movement of the shielding member. The guide structure is an oblique guide groove, an arc guide groove, a curved guide groove, a radial guide groove, an annular guide rail, a segmented guide rail, or a cam-type guide structure.

5. The vertical Bridgeman furnace thermal field control device according to claim 4, characterized in that, The shielding component is a blade, and the upper end face of the central support component is provided with multiple oblique guide grooves, and the lower end face is provided with a slide rail; the two ends of the blade are respectively slidably engaged with the oblique guide grooves and the slide rails, and when the central support component rotates, the blade is driven to retract towards the center or expand outward.

6. The vertical Bridgeman furnace thermal field control device according to claim 5, characterized in that, The blades are no less than two in number, and the blades are fan-shaped plates, arc-shaped plates, trapezoidal plates or fan-shaped annular plates.

7. The vertical Bridgeman furnace thermal field control device according to claim 1, characterized in that, The air pressure regulating hole is configured as one or multiple holes distributed symmetrically along the center or circumference. The air pressure regulating hole is a round hole, an oblong hole, a long hole or a multi-hole array.

8. The vertical Bridgeman furnace thermal field control device according to claim 1, characterized in that, The cooling device includes an inlet, a cooling pipe, and an outlet. The inlet and outlet are located on the side wall of the furnace body, and the cooling pipe is laid on the bottom wall of the furnace body to allow the cooling medium to flow and exchange heat at the bottom of the furnace body.

9. The vertical Bridgeman furnace thermal field control device according to claim 1, characterized in that, A temperature sensor is installed at the output port of the cooling device, and a flow regulating valve is installed at the input port or on the input pipeline.

10. A method for controlling the thermal field using the vertical Bridgeman furnace thermal field control device according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1. Raw material melting stage: Control the opening and closing device to be in the closed state so that the heat is concentrated in the upper part of the furnace body to heat and melt the raw materials in the crucible; S2. Crystal growth stage: Control the opening and closing device to switch to the open state, start the cooling device, and form a low temperature zone at the bottom of the furnace body, which together with the heating device to build a temperature gradient distributed along the axis; at the same time, the crucible is lowered along the axis, and the melt gradually solidifies and grows crystals under the action of the temperature gradient. S3. Thermal field isolation stage: After the crystal growth is completed and it enters the insulation chamber with the crucible, the opening and closing device is switched to the closed state to prevent the residual heat in the upper part of the furnace from being transferred downwards. S4. Cooling control stage: Adjust the cooling intensity of the cooling device and the opening and closing size of the opening and closing device to control the cooling rate of the crystal.

11. The method according to claim 10, characterized in that, The cooling intensity is adjusted by a flow regulating valve installed at the inlet of the cooling device or on the inlet pipeline, and a temperature sensor installed at the outlet of the cooling device.

12. The method according to claim 10, characterized in that, The crystal is a gallium oxide single crystal.

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